Authors :
Presenting Author: Evan Brady, – Emory University
Kelsey Hewitt, PsyD – Emory University School of Medicine; Rebecca Roth, BS – Emory University School of Medicine; taylor Shade, BS – Emory University School of Medicine; Mary Manley, BS – Emory University School of Medicine; Adam Khalef, undergrad – Georgia State University; Miguel Valentin, BS – Case Western University; Arden Godfrey, BS – Emory University School of Medicine; Amanda Eakin, MA – Emory University School of Medicine; Edward Valentin, PhD – Emory University School of Medicine; Emma Acerbo, PhD – Emory University School of Medicine; Adam Dickey, MD – Emory University School of Medicine; Robert Gross, MD, PhD – Emory University School of Medicine; David Loring, PhD – Emory University School of Medicine; Daniel Drane, PhD – Emory University School of Medicine
Rationale: A major goal of neuropsychological testing in the epilepsy surgical setting is to confirm seizure onset localization. Here, we present a novel measure of response inhibition and complex attention, the Letter Alternation Test (LAT), that has the potential to predict cognitive deficits and as well as delineate frontal versus temporal lobe dysfunction in a rather quick, efficient manner.
Methods: The LAT contains two trials, a simple reading trial followed by an alternation trial. In the letter reading trial, patients are presented with two rows of letters (either “A” or “B”) and are asked to simply read the letters as accurately and quickly as possible. In the complex attention trial, patients are asked to respond with the opposite letter (i.e., say “B” when you see “A”). In the current study, the LAT was administered to 50 presurgical epilepsy patients who then completed phase I epilepsy surgical monitoring (i.e., 12 frontal lobe epilepsy [FLE] patients, and 38 temporal lobe epilepsy [TLE] patients) and 51 healthy controls (HCs) (See Table 1). We also administered two other executive function measures (Trailmaking Test [TMT] and Stroop) to explore convergent validity factors for the LAT and its ability to predict group membership. A logistic regression was performed to ascertain the contribution of these tests in classifying patients as TLE or FLE while controlling for age and education.
Results: Both TLE and FLE patients performed significantly worse than HCs on all three executive function measures including the LAT (See Table 2). The logistic regression model was statistically significant, χ
2(5) = 17.7,
p < .003. The model explained 46.7% (Nagelkerke
R2) of the variance in diagnostic group and correctly classified 82.6% of cases. Slower LAT Alternation time (i.e., time taken to respond with the opposite letter than presented) was associated with an increased likelihood of being classified in the FLE subgroup, and this was the only test that was able to classify patients as TLE or FLE.
Conclusions: These results suggest that the LAT is a potentially useful measure of response inhibition and complex attention capable of identifying impairments in executive functioning, as it strongly correlates with existing measures known to assess these domains (i.e., convergent validity). These data also suggest the LAT is useful for distinguishing FLE from TLE since FLE patients had difficulty with all of the executive tasks, but the TLE patients had less difficulty with the LAT. This task appears to outperform currently available tasks in clinical use, perhaps by capitalizing on its simplicity.
Funding: This project was partially funded by NIH/NINDS grants awarded to Dr. Drane (R01 NS088748, K02 NS070960).